A large nuclear war could leave 5 billion people without enough to eat

Simulations of conflict between nuclear powers suggest even a relatively small nuclear war could cause hundreds of millions of people to starve. A larger war could lead to starvation for billions.

In the 1980s, researchers found a nuclear war could ignite firestorms that would send clouds of soot into the stratosphere, which would encircle the world and reflect enough sunlight to cause a “nuclear winter”. Now Lili Xia at Rutgers University in New Jersey and her colleagues have modelled in more detail how a nuclear war might impact the global food system.

The researchers considered how six different scenarios would affect the global climate. The smallest scenario – representing a war between India and Pakistan – involved an exchange of 100 15-kiloton bombs, launching 5 billion kilograms of soot into the atmosphere. The largest scenario – representing an exchange of 4400 100-kiloton bombs between seven countries – created 100 billion kilograms of soot.

The team then modelled how the resulting cooling of the planet and other effects like changing rainfall would affect yields of major crops and marine fisheries in every country.

In the smallest scenario, around 27 million people would be killed by the blasts and 255 million people would starve in the second year after the war. Without accounting for other consequences like ruined infrastructure or radioactive contamination, available calories would decrease by 8 per cent on average globally.

The largest scenario would directly kill 360 million people and leave more than 5 billion people without enough to eat. Nuclear-armed countries at higher latitudes in the northern hemisphere – including the US, UK, France, Russia and China – would experience some of the largest calorie reductions in all scenarios, with cooling having a greater impact on agriculture there than in the tropics.

“Nuclear war is really bad for everyone even if you are far away from it,” says Xia. Last year, leaders of the five nuclear-armed nations mentioned above reaffirmed that “a nuclear war cannot be won and must never be fought”.

The researchers didn’t account for ways people might adapt, such as by eating seaweed or insects, but those changes likely couldn’t happen fast enough, says Xia. Feeding less food to livestock would help prevent starvation only in a few countries in the smallest scenarios. Countries would likely horde resources, which would limit trade, says Alan Robock, also at Rutgers University.

David Shlapak at the RAND Corporation, a US think tank, says the scenarios described in the paper are plausible, though they rely on uncertain estimates of how much soot a nuclear war might actually produce. He says Russia’s invasion of Ukraine as well as tensions around Taiwan and China’s growing nuclear capability have raised a spectre of nuclear conflict not seen since the cold war. “Any nuclear war is a catastrophe beyond reckoning,” he says.